This story was written by CBSNews.com political reporter Brian Montopoli.It's hard to escape the word "change" at a Barack Obama event. It was everywhere at a packed Obama rally at a Des Moines middle school Sunday night: On the placards held up by supporters, the huge banner behind the podium, and the lips of the candidate himself.

"We've talked about change when we were down, we've talked about change when we were up," Obama told the crowd during slowly building, 40-minute speech. "And this change thing must be catching on because I notice now suddenly everybody is talking about change."

Change isn't the only thing everybody is talking about. Like Hillary Clinton, Obama talks about his experience, though he likes to say that his is from outside Washington. Like John Edwards, he adopts a populist mantle, complaining that "we've got C.E.O.s making more in ten minutes than ordinary workers are making in an entire year."

When it comes to the three leading Democrats, in fact, the differences are often articulated in degrees. Edwards, Clinton and Obama have similar positions on the majority of the issues, and as they make their final pitches to Iowa voters, their rhetoric tends to be about who is the most in favor of the working man, who really represents change.

At a Des Moines high school on Saturday night, Edwards was pushing the populist rhetoric hard. With "Steelworkers For Edwards" chanting from the balcony, the candidate, who entered to the strains of John Mellencamp's "Our Country," attacked drug companies, insurance companies, and Exxon/Mobil. (Mellencamp will campaign with Edwards on Jan 2nd, the day before the caucuses.)

Edwards talked about a young woman who died because her health insurance company long refused to pay for a liver transplant. "And they want me to sit at a table and negotiate with these people?," he asked.

Clinton, appearing at an elementary school in Story City, spent the opening portion of her speech stressing her foreign policy bona fides in the wake of the Benazir Bhutto assassination in Pakistan. In discussing her experience, she talked about working "across party lines" in the Senate. "I know how to find common ground, and I know how to stand my ground," said Clinton.

As Obama campaign manager David Plouffe acknowledged during a Monday morning conference call, "there is a lot of fluidity in this [Iowa] race right now." Many polls put the three frontrunners in a statistical dead heat in the state, with perhaps 30 percent of potential caucus-goers still yet to definitively make up their minds. All three are traveling the state in an effort to finish first and garner crucial momentum going into the Jan. 8 New Hampshire primary. Second tier candidates Joe Biden, Bill Richardson, and Chris Dodd are also campaigning here, hoping to earn a better-than-expected finish that keeps them in the picture.

The crowds for the three Democratic frontrunners have been big, not to mention generally more enthusiastic than those at Republican events. "There are just lots of tremendously qualified people," said Nanci Sande, a project manager from Adel. Scott Stricker, a real estate developer who lives in Des Moines, said he is trying to choose between Biden, Clinton, Edwards and Richardson.

"There's a number of good candidates - more so than I can remember in recent elections," he said. "That's why I'm leaning [towards] four [of them]. Normally I'm down to one or two at this point. There have been times when you're struggling to pick one that you feel really strongly about."

The campaigns will tell you that doing well in Iowa is about what's known as "organization" - the ability to make sure you get your voters to their caucuses on a cold night in January. It's a complex operation that involves volunteers knocking on doors and making phone calls, precinct captains encouraging neighbors to show up, and myriad small activities that they hope will raise turnout for their candidate.

You might even say that success in Iowa is as much about logistics as it is about substance. And while all there frontrunners' campaigns claim to have the strongest organization in the state, the Obama and Clinton campaigns have been quietly signaling their concerns about Edwards' strength. Edwards took federal matching funds, and he has fewer financial resources than his two chief rivals. More than Clinton and Obama, he is seen as needing the momentum that comes with winning here.

Edwards has consistently stressed that he hasn't taken money from Washington lobbyists, and he pledged Saturday "that corporate lobbyists or anyone who has lobbied for a foreign government will not be permitted to work in my White House." But Clinton and Obama staffers have been pointing reporters to an oil industry lobbyist named Scott Tyre, who has raised money for the candidate, and suggesting that Edwards is being hypocritical.

Edwards responds to the charges by saying that all his campaign donations are checked against a federal list of lobbyists. An Edwards aide told the Des Moines Register that Tyre could be seen as a state, not federal, lobbyist, noting that state lobbyists are not kept from donating to Edwards.

Obama, meanwhile, has recently undertaken a unique strategy to win a few extra votes. Under Iowa Democratic Party rules, a candidate has to garner 15 percent support at a caucus; if he doesn't get it, his supporters must choose someone who did. Obama is now asking voters if they would consider him as their back up candidate. "Make me your second choice, although you are wiser making me your first," he said in Indianola Monday.

All three leading Democrats are also claiming to be the most likely to beat the Republican nominee in a general election. Clinton says she is "tested and ready" to win the election, and her stump speech includes the line that Republicans have "been after me for 16 years. And much to their dismay, I'm still here." Edwards, Obama and their surrogates, meanwhile, point to polls that they say suggest they are the most electable Democrat.

And while the polls suggest that Clinton, Edwards and Obama will finish in the top three here, there is little consensus on which of them will win, which will place, and which will show on January 3rd. Nicholas Tormey, a psychotherapist from Des Moines, said Sunday he is leaning towards Edwards and Obama. How, he was asked, will he choose between the two?